At this point, "outdated" is a compliment, it means that it has a menu with standard shortcuts, discoverability, accessibility. It means that it won't take 800MB of RAM to provide minimal functionality. It will stay the same across the years and not be subject of experimentation by UI designers thinking that they know better. Postman's UI started so-so and just went worse from there. SoapUI before it offered similar functionality using Swing. It's always the same app, you can rewrite it but there's no reinventing it.